Optoelectronic devices having a dilute nitride layer

ABSTRACT

Optoelectronic devices having GaInNAsSb, GaInNAsBi or GaInNAsSbBi active layers are disclosed. The optoelectronic devices have an active or absorbing layer, with a bandgap within a range from 0.7 eV and 1.2 eV. The active layer is coupled to a multiplication layer. The multiplication layer is designed to provide a large optical gain with a high signal-to-noise ratio at low light levels at wavelengths up to 1.8 μm.

This application claims the benefit under 35 U.S.C. § 119(e) of U.S.Provisional Application No. 62/685,039, filed on Jun. 14, 2018, which isincorporated by reference in its entirety.

FIELD

The disclosure relates to shortwave infrared (SWIR) optoelectronicdevices operating within the wavelength range of 0.9 μm to 1.8 μmincluding photodetectors, photodetector arrays, and avalanchephotodetectors.

BACKGROUND

Optoelectronic devices operating in the infrared wavelength rangebetween 0.9 μm and 1.8 μm range have a wide range of applications,including fiber optic communications, sensing, and imagingTraditionally, compound III-V semiconductor materials are used to makesuch devices. Indium gallium arsenide (InGaAs) materials are usuallygrown on indium phosphide (InP) substrates. The composition andthickness of the InGaAs layers are chosen to provide the requiredfunctionality, such as light emission or absorption at desiredwavelengths of light and are also lattice-matched or very closelylattice-matched to the InP substrate to produce high quality materialsthat have low levels of crystalline defects, and high levels ofperformance.

With respect to photodetectors, devices that can be produced includehigh-speed photodetectors for telecommunications applications, andarrays of photodetectors that can be used as sensors and imagers formilitary, biomedical, industrial, environmental, and scientificapplications. In such applications, photodetectors with highresponsivity, low dark current, and low noise are desirable.

Although InGaAs on InP materials currently dominate the SWIRphotodetector market, the material system has several limitations,including the high cost of InP substrates, low yields due to fragilityof the InP substrates, and limited InP wafer diameter (and associatedquality issues at larger diameters). From a manufacturing perspective,and also from an economic perspective, gallium arsenide (GaAs)represents a better substrate choice. However, the large latticemismatch between GaAs and the InGaAs alloys required for infrareddevices produces poor quality materials that compromise electrical andoptical performance. Attempts have been made at producinglong-wavelength (greater than 1.2 μm) materials for photodetectors onGaAs, based on dilute nitride materials such as GaInNAs and GaInNAsSb.However, where device performance is reported, it has been much poorerthan for InGaAs/InP devices, for example, very low responsivity, whichrenders the materials unsuited for practical sensing and detectionapplications. Other considerations for photodetectors include darkcurrent, and specific responsivity.

For example, Cheah et al., “GaAs-Based Heterojunction p-i-nPhotodetectors Using Pentenary InGaAsNSb as the Intrinsic Layer”, IEEEPhoton. Technol. Letts., 17(9), pp. 1932-1934 (2005), and Loke et al.,“Improvement of GaInNAs p-i-n photodetector responsivity by antimonyincorporation”, J. Appl. Phys. 101, 033122 (2007), report photodetectorshaving a responsivity of only 0.097 A/W at a wavelength of 1300 nm.

Tan et al., “GaInNAsSb/GaAs Photodiodes for Long WavelengthApplications, IEEE Electron. Dev. Letts., 32(7), pp. 919-921 (2011)describe photodiodes having a responsivity of only 0.18 A/W at awavelength of 1300 nm.

In U.S. Application Publication No. 2016/0372624, Yanka et al. discloseoptoelectronic detectors having dilute nitride layers (InGaNAsSb).Although certain parameters that relate to semiconductor materialquality are described, no working detectors having practicalefficiencies are taught within the broad compositional range disclosed.

Co-pending U.S. Application Publication No. 2019/0013430 A1, which isincorporated herein by reference in its entirety, describes dilutenitride detectors having responsivities greater than 0.6 A/W at awavelength of 1300 nm.

In sensing and imaging applications such as environmental monitoring andnight vision, the optical signal levels can be low, and so internal gainprovided by an avalanche photodiode (APD) is desirable. Tan et al. insuggested that GaInNAsSb materials could be used as an absorber layer inGaAs-based APDs, employing an Al_(0.8)Ga_(0.2)As avalanche layer. Inaddition to the multiplication factor of the APD, the noise performanceof the detector is also important. Multiplication can result in excessnoise related to the stochastic or statistical nature of the avalanche(or impact ionization) process. The excess noise factor is a function ofthe carrier ionization ratio, k, where k is usually defined as the ratioof hole to electron ionization probabilities (k≤1). Tan et al., in“Experimental evaluation of impact ionization in dilute nitride GaInNAsdiodes”, Appl. Phys. Lett. 102, 102101 (2013), describe the impactionization process in dilute nitride GaInNAs diodes. For alloys with lownitrogen composition <2%, the asymmetry in ionization coefficients isnot sufficient, and is similar to values reported for GaAs. However,while k could be enhanced by a factor of 4 for compositions with anitrogen content greater than about 2%, suppressed impact ionizationcoefficients limit the ability of those materials to provide adequatemultiplication behavior in an avalanche photodetector.

Thus, to take advantage of the manufacturing scalability and costadvantages of GaAs substrates, there is continued interest in developinglong-wavelength materials on GaAs that have improved optoelectronicperformance, with improved multiplication characteristics and low noisecharacteristics.

SUMMARY

According to the present invention, semiconductor optoelectronic devicescomprise: a substrate; a first barrier layer overlying the substrate; amultiplication layer overlying the first barrier layer; wherein themultiplication layer comprises Ga_(1-x)In_(x)N_(y)As_(1-y-z)(Sb,Bi)_(z),wherein 0≤x≤0.4, 0≤y≤0.07, and 0≤z≤0.2. an active layer overlying themultiplication layer, wherein, the active layer comprises a latticematched or pseudomorphic dilute nitride material; and the dilute nitridematerial has a bandgap within a range from 0.7 eV and 1.2 eV; and asecond barrier layer overlying the active layer.

According to the present invention, methods of forming a semiconductoroptoelectronic devices comprise forming a first barrier layer overlyinga substrate; forming a multiplication layer overlying the first barrierlayer, wherein the multiplication layer comprisesGa_(1-x)In_(x)N_(y)As_(1-y-z)(Sb,Bi)_(z), wherein 0≤x≤0.4, 0≤y≤0.07, and0<z≤0.2; forming an active layer overlying the multiplication layer,wherein, the active layer comprises a pseudomorphic dilute nitridematerial; and the dilute nitride material has a bandgap within a rangefrom 0.7 eV and 1.2 eV; and forming a second barrier layer overlying theactive layer.

BRIEF DESCRIPTION OF THE DRAWINGS

The drawings described herein are for illustration purposes only. Thedrawings are not intended to limit the scope of the present disclosure.

FIG. 1 shows a side view of a semiconductor optoelectronic deviceaccording to the present invention.

FIG. 2 shows a side view of another semiconductor optoelectronic deviceaccording to the present invention.

FIG. 3 shows a side view of another semiconductor optoelectronic deviceaccording to the present invention.

FIG. 4 shows a side view of an avalanche photodetector according to thepresent invention.

FIG. 5 shows a schematic band edge diagram for an avalanche photodiodewith separate absorber, charge and multiplication layers according tothe present invention.

FIGS. 6A and 6B show schematic band edge diagrams of a multiplicationregion having two linearly graded interlayers at zero bias and underreverse bias, respectively.

FIGS. 6C and 6D show schematic band edge diagrams of a multiplicationregion having a single non-linearly graded layer at zero bias.

FIG. 7 shows a schematic band edge diagram for a four-periodsuperlattice multiplication region.

FIG. 8 shows a schematic band edge diagram for a two-period superlatticemultiplication region with step-graded interlayers.

DETAILED DESCRIPTION

The following detailed description refers to the accompanying drawingsthat show, by way of illustration, specific details and embodiments inwhich the invention may be practiced. These embodiments are described insufficient detail to enable those skilled in the art to practice thepresent invention. Other embodiments may be utilized, and structural,logical, and electrical changes may be made without departing from thescope of the invention. The various embodiments disclosed herein are notnecessarily mutually exclusive, as some disclosed embodiments may becombined with one or more other disclosed embodiments to form newembodiments. The following detailed description is, therefore, not to betaken in a limiting sense, and the scope of the embodiments of thepresent invention is defined only by the appended claims, along with thefull scope of equivalents to which such claims are entitled.

The term “lattice matched” as used herein means that the two referencedmaterials have the same lattice constant or a lattice constant differingby up to +/−0.2%. For example, GaAs and AlAs are lattice matched, havinglattice constants differing by 0.12%, and are considered to be latticematched.

The term “pseudomorphically strained” as used herein means that layersmade of different materials with a lattice constant difference up to+/−2% can be grown on top of a lattice matched or strained layer withoutgenerating misfit dislocations. The lattice parameters can differ, forexample, by up to +/−1%, by up to +/−0.5%, or by up to +/−0.2%.

The term “layer” as used herein, means a continuous region of a material(e.g., an alloy) that can be uniformly or non-uniformly doped and thatcan have a uniform or a non-uniform composition across the region.

The term “bandgap” as used herein is the energy difference between theconduction and valence bands of a material.

The term “responsivity” as used herein is the ratio of the generatedphotocurrent to the incident light power at a given wavelength.

FIG. 1 shows a side view of an example of a semiconductor optoelectronicdevice 100 according to the present invention. Semiconductoroptoelectronic device 100 comprises a p-i-n diode and a multiplicationlayer. Device 100 comprises a substrate 102, a first doped layer 104, amultiplication layer 106, an active (or absorber) layer 108, and asecond doped layer 110. For simplicity, each layer is shown as a singlelayer. However, it will be understood that each layer can include one ormore layers with differing compositions, thicknesses, and doping levelsto provide an appropriate optical and/or electrical functionality, andto improve interface quality, electron transport, hole transport and/orother optoelectronic properties. The purpose of the multiplication layer106 is to amplify the photocurrent generated by the active region of aphotodetector device. The structure of device 100 provides an avalanchephotodiode (APD). An APD introduces an additional p-n junction into thestructure, as well as introduces an additional thickness. This allows ahigher reverse bias voltage to be applied to the device, which resultsin carrier multiplication by the avalanche process.

An APD is an example of an optoelectronic device provided by the presentdisclosure. Examples of other optoelectronic devices includephotovoltaic cells, lasers, photodiodes, phototransistors,photomultipliers, single-photon avalanche photodetectors, optoisolators,integrated optical circuits, photoresistors, charge-coupled imagingdevices, quantum cascade lasers, multiple quantum well devices, andoptocouplers. Although APDs are referred to throughout thespecification, it will be understood that the structures, materials, andproperties can be used in other optoelectronic devices.

Substrate 102 can have a lattice constant that matches or nearly matchesthe lattice constant of GaAs or Ge. The substrate can be, for example,GaAs, Ge or a buffered silicon substrate that has a lattice constantapproximately equal to that of GaAs or Ge. Substrate 102 may be dopedp-type, or n-type, or may be a semi-insulating (SI substrate). Thethickness of substrate 102 can be chosen to be any suitable thickness.Substrate 102 can include one or more layers, for example, a Si layerhaving an overlying SiGeSn buffer layer that is engineered to have alattice constant that matches or nearly matches the lattice constant ofGaAs or Ge. This can mean the substrate has a lattice parameterdifferent than that of GaAs or Ge by less than or equal to 3%, less than1%, or less than 0.5% of the lattice constant of GaAs or Ge.

First doped layer 104 can have a doping of one type and the second dopedlayer 210 can have a doping of the opposite type. If first doped layer104 is doped n-type, second doped layer 110 is doped p-type. Conversely,if first doped layer 104 is doped p-type, second doped layer 110 isdoped n-type. Examples of p-type dopants include C and Be. Examples ofn-type dopants include Si and Te. Doped layers 104 and 110 can be chosento have a composition that is lattice matched or pseudomorphicallystrained to the substrate. The doped layers can comprise any suitableIII-V material, such as GaAs, AlGaAs, GaInAs, GaInP, GaInPAs, GaInNAs,GaInNAsSb. The bandgap of the doped layers can be selected to be largerthan the bandgap of active layer 108. Doping levels can be within arange from 1×10¹⁵ cm⁻³ to 2×10¹⁹ cm⁻³. Doping levels may be constantwithin a layer and/or the doping profile may be graded, for example,increasing the doping level from a minimum value to a maximum value as afunction of the distance from the interface between the doped layer andthe active layer. Doped layers 104 and 110 can have a thickness, forexample, within a range from 50 nm and 3 μm.

Active layer 108 can be lattice matched or pseudomorphically strainedwith respect to the substrate and/or to the doped layers. The bandgap ofactive layer 108 can be lower than that of the doped layers 104 and 110.Active layer 108 can comprise a layer capable of processing light over adesired wavelength range. Processing is defined to be a light emission,a light receiving, a light sensing and light modulation.

Active layer 108 can include a dilute nitride material. The dilutenitride material can be Ga_(1-x)In_(x)N_(y)As_(1-y-z)Sb_(z), where x, yand z can be 0≤x≤0.4, 0≤y≤0.07 and 0<z≤0.2, respectively. In someembodiments, x, y and z can be 0.01≤x≤0.4, 0.02≤y≤0.07 and 0.001≤z≤0.04,respectively. Active layer 108 can have a bandgap within a range from0.7 eV to 1.2 eV such that the active layer can absorb or emit light atwavelengths up to 1.8 μm. Bismuth (Bi) may be added as a surfactantduring growth of the dilute nitride, improving material quality (such asdefect density), and the device performance. The thickness of activelayer 108 can be within a range, for example, from 0.2 μm to 10 μm, suchas from 1 μm to 4 μm. Active layer 108 can be compressively strainedwith respect to the substrate 102. Strain can also improve deviceperformance. For a photodetector, the device performance of mostrelevance includes the dark current, operating speed, noise andresponsivity. Active layer 108 can comprise an intrinsic layer or anunintentionally doped layer. Unintentionally doped semiconductors do nothave dopants intentionally added but can include a nonzero concentrationof impurities that act as dopants. The carrier concentration of theactive layer can be, for example, less than 1×10¹⁶ cm⁻³ (measured atroom temperature), less than 5×10¹⁵ cm⁻³, or less than 1×10¹⁵ cm⁻³.However, active layer 108 can be doped close to the interface withoverlying doped layer 110 and/or the underlying multiplication layer 106(or charge layer 207 in FIG. 2). The composition of active layer 108 canalso be increased in a region close to the interface with overlyingdoped layer 110 and/or the multiplication layer 106 (or charge layer 207in FIG. 2). Graded interlayers and doping can reduce potential barriersfor charge carriers, as well as improve carrier extraction from theactive (absorbing) layer.

The multiplication layer 106 can comprise a p-type III-V layer thatamplifies the current generated by the active layer 108 throughavalanche multiplication. Thus, for each free carrier (electron or hole)generated by the active layer 108, the multiplication layer 106generates one or more carriers via the avalanche effect. Thus, themultiplication layer 106 increases the total current generated by thesemiconductor 100. Multiplication layer 106 can comprise a III-Vmaterial, such as GaAs, or AlGaAs, AlInGaP, or a dilute nitride such asGaInNAsSb, comprising Ga_(1-x)In_(x)N_(y)As_(1-y-z)Sb_(z), where x, yand z can be 0≤x≤0.4, 0≤y≤0.07 and 0<z≤0.2. As will be explained,multiplication layer 106 can comprise more than one layer with more thanone composition, or with a graded composition in order to improve theoptoelectronic performance of the device. Multiplication layer 106 cancomprise an intrinsic layer or an unintentionally doped layer.Unintentionally doped semiconductors do not have dopants intentionallyadded but can include a nonzero concentration of impurities that act asdopants. The carrier concentration of the multiplication layer can be,for example, less than 1×10¹⁶ cm⁻³ (measured at room temperature), lessthan 5×10¹⁵ cm⁻³, or less than 1×10¹⁵ cm⁻³. However, multiplicationlayer 106 can be doped close to the interface with overlying activelayer 110 (or charge layer 207 in FIG. 2), and/or the underlying firstdoped layer 104. The thickness of multiplication layer 106 can be withina range from 0.05 μm to 1.5 μm.

FIG. 2 shows a side view of an example of a semiconductor optoelectronicdevice 200 according to the present invention. Device 200 is similar todevice 100, but it has an additional charge layer 207 overlying themultiplication layer 206 and underlying active layer 208. A narrowerbandgap dilute nitride material as the active layer 208 can produce moredark current under operation, since a high field required formultiplication can also cause tunneling between bands. Charge layer 207has a larger bandgap than active layer 208 and is also doped to controlthe potential across the absorption material, so that only themultiplication layer experiences a very high electric field. Chargelayer 207 can comprise a III-V material that has a larger bandgap thanactive layer 206, such as GaAs, or AlGaAs, AlInGaP, or a dilute nitridesuch as Ga_(1-x)In_(x)N_(y)As_(1-y-z)Sb_(z), where x, y and z can be0≤x≤0.4, 0≤y≤0.07 and 0<z≤0.2, or where x, y and z can be 0≤x≤0.4,0≤y≤0.07 and 0<z≤0.04. The thickness of charge layer 207 and the dopinglevel of charge layer 207 provide a total charge in the charge layer.The total charge can be chosen to minimize the field across active layer208 when the APD is operating at a high electric field close to thebreakdown condition for the multiplication layer 206, while ensuring thefield across absorption layer 208 is strong enough for efficientcollection of photogenerated charge carriers. The total charge of chargelayer 207 also ensures that the “punch-through” operating condition,i.e., the bias at which the depletion region reaches the absorptionlayer, occurs at a suitable voltage or field that allows the onset ofamplification. The thickness of charge layer 207 can be within a range,for example, from 0.1 μm to 1 μm. The doping level of charge layer 207can be between 1×10¹⁷ cm⁻¹ and 5×10¹⁸ cm⁻³.

FIG. 3 shows a side view of an example of a semiconductor optoelectronicdevice 300 according to the present invention. Device 300 is similar todevice 200, but each of the doped layers are shown to comprise twolayers. Device 300 includes a substrate 302, a first contact layer 304a, a first barrier layer 304 b, a multiplication layer 306, a chargelayer 307, an active layer 308, a second barrier layer 310 a, and asecond contact layer 310 b.

Substrate 302 can have a lattice constant that matches or nearly matchesthe lattice constant of GaAs or Ge. The substrate can be GaAs. Substrate302 may be doped p-type, or n-type, or may be a semi-insulating (SI)substrate. The thickness of substrate 302 can be chosen to be anysuitable thickness. Substrate 302 can include one or more layers, forexample, substrate 302 can include a Si layer having an overlying SiGeSnbuffer layer that is engineered to have a lattice constant that matchesor nearly matches the lattice constant of GaAs or Ge. This can mean thesubstrate can have a lattice parameter different than that of GaAs or Geby less than or equal to 3%, less than 1%, or less than 0.5% of GaAs orGe.

First contact layer 304 a and first barrier layer 304 b provide a firstdoped layer 305, having a doping of one type, and second barrier layer310 a and second contact layer 310 b provide a second doped layer 309,having a doping of the opposite type. If first doped layer 305 is dopedn-type, second doped layer 309 is doped p-type. Conversely, if firstdoped layer 305 is doped p-type, second doped layer 309 is doped n-type.Examples of p-type dopants include C and Be. Examples of n-type dopantsinclude Si and Te. Doped layers 305 and 309 can be chosen to have acomposition that is lattice matched or pseudomorphically strained to thesubstrate. The doped layers can comprise any suitable III-V material,such as, for example, GaAs, AlGaAs, GaInAs, GaInP, GaInPAs, GaInNAs,GaInNAsSb. The contact and barrier layers can have differentcompositions and different thicknesses. The bandgap of the doped layerscan be selected to be larger than the bandgap of active region 306. Thedoping level of first contact layer 304 a can be chosen to be higherthan the doping level of first barrier layer 304 b. A higher dopingfacilitates electrical connection with a metal contact. Similarly, thedoping level of second contact layer 310 b can be chosen to be higherthan the doping level of second barrier layer 310 a. Higher dopinglevels facilitate electrical connection with a metal contact. Dopinglevels can be, for example, within a range from 1×10¹⁵ cm⁻³ to 2×10¹⁹cm⁻³. Doping levels may be constant within a layer and/or the dopingprofile may be graded, for example, increasing the doping level from aminimum value to a maximum value as a function of the distance from theinterface between the doped layer and the active layer. Each of layers304 a, 304 b, 310 a and 310 b can have a thickness, for example, withina range from 50 nm to 3 μm.

The multiplication layer 306 can comprise a p-type III-V layer thatamplifies the current generated by the active layer 308 throughavalanche multiplication. Thus, for each free carrier (electron or hole)generated by the active layer 308, the multiplication layer 306generates one or more carriers via the avalanche effect. Thus, themultiplication layer 306 increases the total current generated by thesemiconductor 300. Multiplication layer 306 can comprise a III-Vmaterial, such as GaAs, or AlGaAs, AlInGaP, or a dilute nitride such asGa_(1-x)In_(x)N_(y)As_(1-y-z)Sb_(z), where x, y and z can be 0≤x≤0.4,0≤y≤0.07 and 0<z≤0.2. As will be explained, multiplication layer 306 cancomprise more than one layer with a different composition, or with agraded composition in order to improve the optoelectronic performance ofthe device. Multiplication layer 306 can comprise an intrinsic layer oran unintentionally doped layer. Unintentionally doped semiconductors donot have dopants intentionally added but can include a nonzeroconcentration of impurities that act as dopants. The carrierconcentration of the multiplication layer 306 can be, for example, lessthan 1×10¹⁶ cm⁻³ (measured at room temperature), less than 5×10¹⁵ cm⁻³,or less than 1×10¹⁵ cm⁻³. However, multiplication layer 306 can be dopedclose to the interface with overlying charge layer 307, and/or theunderlying first barrier layer 304 b. The thickness of multiplicationlayer 306 can be within a range from 0.05 μm to 1.5 μm.

Charge layer 307 can be a doped III-V layer has a larger bandgap thanactive layer 308 and is also doped to control the potential across theabsorption material, so that only the multiplication layer 306experiences a very high electric field. Charge layer 307 can comprise aIII-V material that has a larger bandgap than active layer 306, such asGaAs, or AlGaAs, AlInGaP, or a dilute nitride such asGa_(1-x)In_(x)N_(y)As_(1-y-z)Sb_(z), where x, y and z can be 0≤x≤0.4,0≤y≤0.07 and 0<z≤0.2, or where x, y and z can be 0≤x≤0.4, 0≤y≤0.07 and0<z≤0.04. The thickness of charge layer 307 and the doping level ofcharge layer 307 provide a total charge in the charge layer. The totalcharge can be chosen to minimize the field across active layer 308 whenthe APD is operating at a high electric field close to the breakdowncondition for the multiplication layer 306, while ensuring the fieldacross absorption layer 308 is strong enough for efficient collection ofphotogenerated charge carriers. The total charge of charge layer 307also ensures that the “punch-through” operating condition, the bias atwhich the depletion region reaches the absorption layer, occurs at asuitable voltage or field that allows the onset of amplification. Thethickness of charge layer 307 can be within a range from 0.1 μm to 1 μm.The doping level of charge layer 307 can be between 1×10¹′ cm⁻³ and5×10¹⁸ cm⁻³.

Active layer 308 can be lattice matched or pseudomorphically strainedwith respect to the substrate and/or to the doped layers. The bandgap ofactive layer 308 can be lower than that of layers 304 a, 304 b, 310 aand 310 b. Active layer 308 can comprise a layer capable of processinglight over a desired wavelength range. Processing is defined to be alight emission, a light receiving, a light sensing and light modulation.Active layer 308 can include a dilute nitride material. The dilutenitride material can be Ga_(1-x)In_(x)N_(y)As_(1-y-z)Sb_(z), where x, yand z can be 0≤x≤0.4, 0≤y≤0.07 and 0<z≤0.2, respectively. In someembodiments, x, y and z can be 0.01≤x≤0.4, 0.02≤y≤0.07 and 0.001≤z≤0.04,respectively. Active layer 308 can have a bandgap within a range from0.7 eV to 1.2 eV such that the active layer can absorb or emit light atwavelengths up to 1.8 μm. Bismuth (Bi) may be added as a surfactantduring growth of the dilute nitride, improving material quality (such asdefect density), and the device performance. The thickness of activelayer 308 can be, for example, within a range from 0.2 μm to 10 μm orfrom 1 μm to 4 μm. Active layer 308 can be an intrinsic layer or anunintentionally doped layer. Unintentionally doped semiconductors do nothave dopants intentionally added but can include a non-zeroconcentration of impurities that act as dopants. The carrierconcentration of the active layer 308 can be, for example, less than1×10¹⁶ cm⁻¹ (measured at room temperature), less than 5×10¹⁵ cm⁻³, orless than 1×10¹⁵ cm⁻³. However, active layer 308 can be doped close tothe interface with overlying second barrier layer 310 a and/or theunderlying charge layer 307. The composition of active layer 308 canalso be increased in a region close to the interface with overlyingsecond barrier layer 310 a and/or the underlying charge layer 307 inFIG. 2. Active layer 308 can be compressively strained with respect tothe substrate 302. Strain can also improve device performance. For aphotodetector, the parameters most relevant to device performanceinclude the dark current, operating speed, noise and responsivity.

FIG. 4 Shows a side view of an example of a photodetector 400 accordingto the present invention. Device 400 is similar to device 300. Comparedto device 300, additional device layers include a first metal contact412, a second metal contact 414, a passivation layer 416, and anantireflection coating 418. The semiconductor layers 402, 404 a, 404 b,406, 407, 408, 410 a and 410 b correspond to layers 302, 304 a, 304 b,306, 307, 308, 310 a and 310 b of device 300, respectively. Multiplelithography and materials deposition steps may be used to form the metalcontacts, passivation layer, and antireflection coating. The devicestructure has a mesa structure, produced by etching. This exposes theunderlying layers. A passivation layer 416 is provided that covers theside-walls of the device and exposed surfaces of the semiconductorlayers so as to reduce effects of surface defects and dangling bondsthat may otherwise affect device performance. The passivation layer canbe formed using a dielectric material such as silicon nitride, siliconoxide, or titanium oxide. Anti-reflection layer 418 overlies a firstportion of second contact layer 410 b. The antireflection layer 418 canbe formed using a dielectric material such as silicon nitride, siliconoxide, or titanium oxide. A first metal contact 412 overlies a portionof the first contact layer 404 a. A second metal contact 410 b overliesa portion of second barrier layer 410 a. Metallization schemes forcontacting to n-doped and p-doped materials are known to thoseordinarily skilled in the art. Exemplary photodetector 400 isilluminated from the top surface of the device, i.e. through theinterface between anti-reflection coating 418 and air.

FIG. 5 shows a schematic band edge diagram for an avalanchephotodetector with separate absorber, charge and multiplication layers,in accordance with the present invention. The conduction band and thevalence band are both shown. The semiconductor layers 505, 506, 507,508, 510 a and 510 b correspond to layers 302, 305 306, 307, 308, 310 aand 310 b of device 300 in FIG. 3, respectively. Additionally, a gradinglayer 509 overlies charge layer 507 and underlies active layer 508.Grading layer 509 comprises Ga_(1-x)In_(x)N_(y)As_(1-y-z)Sb_(z), wherex, y and z can be 0≤x≤0.4, 0≤y≤0.07 and 0<z≤0.2, respectively. In someembodiments, x, y and z can be 0.01≤x≤0.4, 0.02≤y≤0.07 and 0.001≤z≤0.04,respectively. Grading layer 509 can have a larger bandgap than activelayer 508 and a bandgap less than or equal to the bandgap of chargelayer 507. Grading layer 509 and can have a fixed composition, or acomposition that increases the bandgap from the interface with absorbinglayer 508 and charge layer 507. Grading layer 509 can also be doped.Grading layer 509 can facilitate extraction of the photogeneratedcarriers from active layer 508. The conduction and valence bands foractive layer 508 are shown as flat. However, active layer 508 can have abackground carrier concentration, for example, less than 1×10¹⁶ cm⁻³(measured at room temperature (23° C.)), less than 5×10¹⁵ cm⁻³, or lessthan 1×10¹⁵ cm⁻³, which can introduce a small tilt the band edges inpractical devices.

In embodiments shown, the charge layer is a separate layer from theactive layer and the multiplication layer. In some embodiments, thecharge layer can be formed close to the interface between themultiplication layer and the active layer and/or grading layer. Thecharge layer can be formed, for example by composition and/or dopinggrades at the active layer and/or grading layer proximate to themultiplication layer.

In one example, APDs with an absorbing layer of GaInNAsSb and an AlGaAsmultiplication layer can be fabricated on a GaAs substrate. Themultiplication layer can be a low noise Al_(0.80)Ga_(0.20)Asmultiplication layer or a superlattice structure, such as GaAs/AlGaAs. Acharge layer can be used between the narrow bandgap absorber and themultiplication layer. The thickness and doping levels for the avalancheregion of the photodetector can be chosen based on desired deviceoperating parameters including the desired multiplication (gain),frequency bandwidth, and operating voltage. Using MOCVD growth, a firstcontact layer of GaAs can be formed on an underlying substrate, having athickness between 0.5 μm and 1 μm, and a n-type doping level between1×10¹⁸ cm⁻³ and 5×10¹⁸ cm⁻³. The first barrier layer overlies the firstcontact layer and is a n-doped Al_(0.80)Ga_(0.20)As layer with athickness between 0.1 μm and 0.2 μm, and a doping level of 1×10¹⁸ cm⁻³.An undoped Al_(0.80)Ga_(0.20)As layer with a thickness between 50 nm and1.5 μm (and preferably between 50 nm and 200 nm) forms themultiplication layer and overlies the first barrier layer. A p-dopedAl_(0.80)Ga_(0.20)As layer with a thickness between 50 nm and 250 nm anda doping level between 1×10¹⁷ cm⁻³ and 1×10¹⁸ cm⁻³ overlies themultiplication layer. This is optionally capped by a GaAs layer between1 nm and 10 nm thick, and having a doping level between 1×10¹⁷ cm⁻³ and1×10¹⁸ cm⁻³. The p-doped AlGaAs layer and optional GaAs cap form thecharge layer. In an alternative embodiment, p-doped InGaP can be used toform the charge layer. After growth of at least a portion of the chargelayer (including any GaAs cap), the epiwafer is transferred to an MBEchamber for subsequent growth of the dilute nitride absorber layer. TheGaAs layer is completed (as required) before an undoped GaInNAsSb activelayer is formed overlying the charge layer, having a thickness within arange from 0.5 μm to 1.5 μm. The second barrier layer is a p-doped GaAslayer with a thickness between 0.1 μm and 0.2 μm, and a doping level of1×10¹⁸ cm⁻³. The second contact layer is a p-doped GaAs layer with athickness between 50 nm and 100 nm and a doping level of between 1×10¹⁸cm⁻³ and 1×10¹⁹ cm⁻³. The strain of the dilute nitride layer can becharacterized using high-resolution X-ray diffraction (XRD). The layercan exhibit a peak splitting between the substrate and dilute nitridelayer in the within a range from −600 arcsec to −1000 arcsec,corresponding to a compressive strain of 0.2% to 0.35%. Devices withactive (absorbing) layers with compressive strain up to 0.4% are alsopossible.

A multiplication layer can comprise a single layer or can comprise twoor more interlayers. The material composition within a multiplicationlayer or interlayer can be constant across the thickness of the layer orinterlayer or can vary across the thickness of the layer or interlayer.Similarly, the bandgap within a multiplication layer or interlayer canbe constant across the thickness of the layer or interlayer or can varyacross the thickness of the layer or interlayer. For example, thematerial composition and bandgap across the thickness of a layer orinterlayer can vary linearly. The bandgap within a linearly graded layeror interlayer can have a minimum bandgap and a maximum bandgap. Forexample, the minimum bandgap can be within a range from 0.7 eV to 1.3eV, and the maximum bandgap can be within a range from 0.8 eV to 1.42eV. The difference between the minimum bandgap and the maximum bandgapcan be, for example, from 100 meV to 600 meV, from 400 meV to 600 meV,or from 200 meV to 500 meV.

A multiplication layer can comprise one or more interlayers. Each of theone or more interlayers can independently compriseGa_(1-x)In_(x)N_(y)As_(1-y-z)(Sb,Bi)_(z). Each of the one or moreinterlayers can have a material composition and bandgap that issubstantially constant across the thickness of the interlayer. Amultiplication layer comprising two or more interlayers can becharacterized by an interlayer having a minimum bandgap, and aninterlayer having a maximum bandgap. For example, the minimum bandgapcan be within a range from 0.7 eV to 1.3 eV, and the maximum bandgap canbe within a range from 0.8 eV to 1.42 eV. The difference between theminimum bandgap and the maximum bandgap can be, for example, from 100meV to 600 meV, from 400 meV to 600 meV, or from 200 meV to 500 meV.

A multiplication layer can comprise one or more interlayers. Each of theone or more interlayers can independently compriseGa_(1-x)In_(x)N_(y)As_(1-y-z)(Sb,Bi)_(z). Each of the one or moreinterlayers can have a material composition and bandgap that is linearlygraded across the thickness of the interlayer. A multiplication layercomprising two or more interlayers can be characterized by an interlayerhaving a minimum bandgap, and an interlayer having a maximum bandgap.For example, the minimum bandgap can be within a range from 0.7 eV to1.3 eV, and the maximum bandgap can be within a range from 0.8 eV to1.42 eV. The difference between the minimum bandgap and the maximumbandgap can be, for example, from 100 meV to 600 meV, from 400 meV to600 meV, or from 200 meV to 500 meV.

A multiplication layer can comprise one or more interlayers having aconstant bandgap, one or more interlayers having a linearly gradedbandgap, or a combination thereof.

In another example, APDs with an active layer of GaInNAsSb and aGaInNAsSb multiplication layer can be fabricated on a GaAs substrate. Afirst contact layer of GaAs or AlGaAs can be formed overlying thesubstrate having a thickness between 0.5 μm and 1 μm, and a n-typedoping level between 1×10¹⁸ cm⁻¹ and 5×10¹⁸ cm⁻³. The first barrierlayer overlies the first contact layer and is a n-doped GaInNAsSb layerwith a thickness between 0.1 μm and 0.2 μm, and a doping level between1×10¹⁸ cm⁻³ and 2×10¹⁸ cm⁻³. An undoped GaInNAsSb layer with a thicknessbetween 50 nm and 1 μm (and preferably between 50 nm and 200 nm) formsthe multiplication layer and overlies the first barrier layer. A p-dopedGaInNAsSb layer with a thickness between 50 nm and 250 nm and a dopinglevel between 1×10¹⁷ cm⁻³ and 1×10¹⁸ cm⁻³ overlies the multiplicationlayer and forms the charge layer. The bandgap of the charge layer islarger than the bandgap of the overlying active layer. In someembodiments, the charge layer comprisesGa_(1-x)In_(x)N_(y)As_(1-y-z)Sb_(z), where x, y and z can be 0≤x≤0.4,0≤y≤0.07 and 0<z≤0.2, respectively. In some embodiments, the chargelayer comprises GaN_(v)As_(1-v-w)Sb_(w), where 0≤v≤0.03 and 0≤w≤0.1. Insome embodiments, the charge layer comprises AlInGaP or InGaP, latticematched or pseudomorphically strained to the substrate. An undopedGaInNAsSb active (or absorber) layer is formed overlying the chargelayer, having a thickness within a range from 0.5 μm to 1.5 μm. Thesecond barrier layer overlies the active layer and is a p-doped GaAs orAlGaAs layer with a thickness between 0.1 μm and 0.2 μm, and a dopinglevel of 1×10¹⁸ cm⁻³. The second contact layer is a p-doped GaAs orAlGaAs layer with a thickness between 50 nm and 100 nm and a dopinglevel of between 1×10¹⁸ cm⁻³ and 1×10¹⁹ cm⁻³. The strain of the dilutenitride layer can be characterized using high-resolution X-raydiffraction (XRD). The layer can exhibit a peak splitting between thesubstrate and dilute nitride layer in the within a range from −600arcsec to −1000 arcsec, corresponding to a compressive strain of 0.2% to0.35%. Devices with active (absorbing) layers with compressive strain upto 0.4% are also possible.

In another example, a dilute nitride multiplication layer can be usedthat has a step-like or graded band structure, having multiple layerswith different compositions. While the gain provided by an APD canprovide higher sensitivity than p-i-n photodiodes, the noise performanceof the detector is also important. Multiplication can result in excessnoise related to the stochastic or statistical nature of the avalanche(or impact ionization) process. The excess noise factor F(M) is afunction of the carrier ionization ratio, k, where k is usually definedas the ratio of hole to electron ionization probabilities (k≤1). In aconventional APD, impact ionization can occur relatively uniformlyacross the multiplication layer. Alternative multiplication regions forAPDs, such as staircase APDs have been proposed in other materialsystems as one way to achieve low noise and make use of bandgapdiscontinuities that cause the avalanche process to occur proximate tosudden bandgap changes. As electrons in a wider bandgap region move intoa narrower bandgap region, their excess energy enables immediate impactionization. As a result, the gain process is more deterministic, whichcan reduce gain fluctuations and reduce excess noise. However, theAlGaAs material system has inadequate band offsets, with approximately60% of the band offset between GaAs and AlGaAs accommodated in theconduction band (i.e., the conduction band offset) and approximately 40%accommodated in the valence band (i.e., the valence band offset). Impactionization can occur for both electrons and holes, which can lead toincreased noise. Furthermore, the material changes from having a directbandgap to having an indirect bandgap for alloy compositions with an Alfraction (of group III atoms) of about 45%, limiting the maximum bandoffset. Consequently, it is difficult to achieve reduced noisecharacteristics. The use of dilute nitride materials such as GaInNAsSb,GaInNAs, GaInNAsSbBi and GaInNAsBi, lattice matched or pseudomorphicallystrained with respect to a substrate can allow larger bandgap changeswithout a transition from a direct to indirect bandgap, and with largerconduction band offsets than achievable with AlGaAs materials. Theinclusion of nitrogen in the alloy introduces a significant bandgapbowing that reduces the bandgap of the dilute nitride material, which,in addition to the inclusion of indium in the alloy, introduces a largerfraction of the band offset in the conduction band (increasing theconduction band offset ratio) and reduces the valence band offset ratio.The larger difference between the conduction band offset and the valenceband offset can enhance the ionization ratio asymmetry between electronsand holes. Dilute nitride materials can therefore be used to improve thenoise performance of staircase and other graded composition avalancheregions of APDs grown on GaAs substrates.

FIG. 6A and FIG. 6B show band edge diagrams for a staircasemultiplication region having a continuously graded composition at zerobias and under reverse bias, respectively. By way of example, two gradedregions are shown, each graded region having a linearly graded bandgap.However, different numbers of graded regions may be used and differentgraded bandgap profiles may also be used, such as a non-linearly gradedbandgap as shown in FIGS. 6C and 6D. The multiplication region cancomprise at least one graded region overlying the first barrier andcontact layers and underlying the charge layer. As a photogeneratedelectron, created by absorption of a photon in the absorbing layer,moves from the wide bandgap region (with bandgap E_(g2)) into the narrowbandgap region (with bandgap E_(g1)), the excess energy enablesimmediate impact ionization to occur. The graded region then allows thecarriers to move across to the next bandgap discontinuity at whichimpact ionization next occurs. The material forming the largest bandgapregion can comprise Ga_(1-p)In_(p)N_(q)As_(1-q-r)Sb_(r), where p, q andr can be 0≤p≤0.4, 0≤q≤0.07 and 0<r≤0.2, respectively. In someembodiments, the largest bandgap region can comprise an In-free materialGaN_(v)As_(1-v-w)Sb_(w), where 0≤v≤0.03 and 0≤w≤0.1, or can compriseGaAs. The material forming the narrowest bandgap comprisesGa_(1-x)In_(x)N_(y)As_(1-y-z)Sb_(z), where x, y and z can be 0≤x≤0.4,0≤y≤0.07 and 0<z≤0.2, respectively. In some embodiments, x, y and z canbe 0.01≤x≤0.4, 0.02≤y≤0.07 and 0.001≤z≤0.04, respectively. The additionof Sb in the widest bandgap material causes the valence band to shiftupwards faster than any shift in the conduction band and can thereforereduce the portion of the bandgap offset in the valance band andincrease the portion of the bandgap offset in the conduction band, atthe interface with the narrower bandgap material. In some embodiments,the bandgap difference between E_(g1) and E_(g2) can be about 600 meV.In some embodiments, the bandgap difference can be between 100 meV and500 meV, or can be between 200 meV and 400 meV. The thickness of agraded region can be between 50 nm and 500 nm, and more than one gradedregion may be used to form the multiplication region.

Practically, growing a dilute nitride material with a linearly gradedbandgap can be challenging, requiring controlled changes in growthrates, and/or growth temperature to modify the N-incorporation. Duringthe growth of a graded dilute nitride material, the flux ratio of theeffusion cells can be changed linearly between the values required forthe beginning composition and the end composition. This can be achievedfor example, by changing the Ga flux during growth. By lowering the Gaflux, while leaving the In, As, Sb and N fluxes the same, the In/Garatio is increased during growth due to the changed group-III fluxratio. The N/As ratio also increases due to the lower growth rate andthe near-unity sticking coefficient for N. The increasing In and Nfractions in the semiconductor alloy allow a decrease in the materialbandgap while also keeping the lattice constant relatively close to thatof GaAs.

An alternative design to a continuously graded bandgap profile, such asa linearly graded bandgap profile or a non-linearly graded bandgapprofile, is a superlattice design, using alternating thin layers withdifferent bandgaps and compositions. This is shown in FIG. 7, where themultiplication region comprises at least one superlattice structureoverlying the first barrier and contact layers and underlying the chargelayer. The bandgap of the charge layer and the underlyingbarrier/contact layer is shown to have a bandgap E_(g2). In themultiplication layer, the widest bandgap material comprisesGa_(1-p)In_(p)N_(q)As_(1-q-r)Sb_(r), where p, q and r can be 0≤p≤0.4,0≤q≤0.07 and 0<r≤0.2, respectively, and has a bandgap E_(g3) which maybe equal to or lesser than E. In some embodiments, the largest bandgapregion of the multiplication layer can comprise an In-free materialGaN_(v)As_(1-v-w)Sb_(w), where 0≤v≤0.03 and 0≤w≤0.1, or can compriseGaAs. The material forming the narrowest bandgap comprisesGa_(1-x)In_(x)N_(y)As_(1-y-z)Sb_(z), where x, y and z can be 0≤x≤0.4,0<y≤0.07 and 0<z≤0.2, respectively, and has a bandgap E_(g1) less thanE_(g2). In some embodiments, x, y and z can be 0.01≤x≤0.4, 0.02≤y≤0.07and 0.001≤z≤0.04, respectively. These layers form a superlattice. Theinclusion of Sb in widest bandgap material causes valence band to shiftupwards faster than conduction band and can therefore reduce the portionof the bandgap offset in the valance band and increase the portion ofthe bandgap offset in the conduction band. In some embodiments, thebandgap difference between E_(g1) and E_(g3) can be about 600 meV. Insome embodiments, the bandgap difference can be between 100 meV and 500meV, or can be between 200 meV and 400 meV. The thickness of eachsuperlattice layer, independently, can be, for example, between 10 nmand 200 nm. A growth pause can be implemented at each composition stepchange within the superlattice. A composition gradient can exist at eachcomposition step within the structure, which can assist in carriertransport across the heterostructures.

In some embodiments, the superlattice design can have a transition fromthe narrow bandgap material to the wide bandgap material, which can beachieved through several steps with different compositions and bandgaps.This can assist with carrier transport and help reduce trapping inwell-like regions. A design example is shown in FIG. 8. In this examplethe wide bandgap material has a bandgap E_(g2), the narrow bandgapmaterial has a bandgap E_(g1), and an intermediate step layer betweenthe wide and narrow bandgap materials has a bandgap E_(g3) betweenE_(g1) and E_(g2). In this example, a single step is shown. However, itwill be understood that multiple steps can also be used, each stephaving a different bandgap intermediate between E_(g1) and E_(g2), withthe bandgaps of the steps arranged in increasing bandgap order betweenE_(g1) and E_(g2). For example, a second step may have a bandgap E_(g4).A stepped structure can be used to approximate a linear grade, as shownin FIGS. 6A and 6B. The bandgap difference between E_(g1) and E_(g2) canbe, for example, between 100 meV and 600 meV, or can be between 200 meVand 400 meV. The thickness of each superlattice layer, independently,can be between 10 nm and 200 nm. Growth pauses can be implemented ateach composition step change. The bandgap step size can be chosen basedon the number of steps and the bandgap difference between E_(g1) andE_(g2). In some embodiments, the bandgap step size between adjacentlayers is approximately the same. A composition gradient can exist ateach composition step within the structure, which can assist in carriertransport across the heterostructures.

The charge layer overlies the multiplication layer and can compriseGa_(1-x)In_(x)N_(y)As_(1-y-z)Sb_(z), where x, y and z can be 0≤x≤0.4,0≤y≤0.07 and 0≤z≤0.2, respectively. In some embodiments, the chargelayer comprises GaN_(v)As_(1-v-w)Sb_(w), where 0≤v≤0.03 and 0≤w≤0.1. Insome embodiments, the charge layer comprises AlGaAs, AlInGaP or InGaPlattice matched or pseudomorphically strained to the substrate.

In devices provided the present disclosure, the dilute nitride layer canhave a minority carrier lifetime, for example, of 1 ns or greater,greater than 1 ns, from 1.1 ns to 4 ns, from 1.1 ns to 3 ns, or from 1.1ns to 2.5 ns, measured at an excitation wavelength of 970 nm, with anaverage CW power of 0.250 mW, and a pulse duration of 200 fs at arepetition rate of 250 kHz generated by a Ti:Sapphire:OPA laser.

To fabricate optoelectronic devices provided by the present disclosure,a plurality of layers is deposited on a substrate in at least onematerials deposition chamber. The plurality of layers may include activelayers, doped layers, contact layers, etch stop layers, release layers,i.e., layers designed to release the semiconductor layers from thesubstrate when a specific process sequence, such as chemical etching, isapplied, buffer layers, or other semiconductor layers.

The plurality of layers can be deposited by molecular beam epitaxy (MBE)or by metal-organic chemical vapor deposition (MOCVD). Combinations ofdeposition methods may also be used.

A semiconductor optoelectronic device can be subjected to one or morethermal annealing treatments after growth. For example, a thermalannealing treatment can include the application of a temperature of 400°C. to 1000° C. for from 10 seconds to 10 hours. Thermal annealing may beperformed in an atmosphere that includes air, nitrogen, arsenic, arsine,phosphorus, phosphine, hydrogen, forming gas, oxygen, helium and anycombination of the preceding materials.

ASPECTS OF THE INVENTION

The invention is further defined by the following aspects.

Aspect 1. A semiconductor optoelectronic device, comprising: asubstrate; a first barrier layer overlying the substrate; amultiplication layer overlying the first barrier layer; wherein themultiplication layer comprises Ga_(1-x)In_(x)N_(y)As_(1-y-z)(Sb,Bi)_(z),wherein 0≤x≤0.4, 0≤y≤0.07, and 0≤z≤0.2, an active layer overlying themultiplication layer, wherein, the active layer comprises a latticematched or pseudomorphic dilute nitride material; and the dilute nitridematerial has a bandgap within a range from 0.7 eV and 1.2 eV; and asecond barrier layer overlying the active layer.

Aspect 2. The device of aspect 1, wherein each of the first barrierlayer and the second barrier layer independently comprises a doped III-Vmaterial.

Aspect 3. The device of any one of aspects 1 to 2, wherein the substratecomprises GaAs, AlGaAs, Ge, SiGeSn, or buffered Si.

Aspect 4. The device of any one of aspects 1 to 3, further comprising acharge layer overlying the multiplication layer and underlying theactive layer.

Aspect 5. The device of any one of aspects 1 to 4, wherein the activelayer has a compressive strain within a range from 0% and 0.4%.

Aspect 6. The device of any one of aspects 1 to 5, wherein the activelayer has a minority carrier lifetime of 1 ns or greater, measured at anexcitation wavelength of 970 nm, with an average CW power of 0.250 mW,and a pulse duration of 200 fs at a repetition rate of 250 kHz generatedby a Ti:Sapphire:OPA laser.

Aspect 7. The device of any one of aspects 1 to 6, wherein the activelayer has a lattice constant substantially the same as the latticeconstant of GaAs or Ge.

Aspect 8. The device of any one of aspects 1 to 7, wherein the activelayer comprises GaInNAs, GaNAsSb, GaInNAsSb, GaInNAsBi, GaNAsSbBi,GaNAsBi, or GaInNAsSbBi.

Aspect 9. The device of any one of aspects 1 to 8, wherein the activelayer comprises Ga_(1-x)In_(x)N_(y)As_(1-y-z)(Sb,Bi)_(z), wherein0≤x≤0.4, 0<y≤0.07, and 0<z≤0.2.

Aspect 10. The device of any one of aspects 1 to 9, wherein the activelayer has a thickness within a range from 0.2 μm to 10 μm.

Aspect 11. The device of any one of aspects 1 to 10, wherein themultiplication layer comprises a linearly graded bandgap across thethickness of the layer and is characterized by a minimum bandgap and amaximum bandgap.

Aspect 12. The device of aspect 11, wherein the minimum bandgap iswithin a range from 0.7 eV to 1.3 eV and the maximum bandgap is within arange from 0.8 eV to 1.42 eV.

Aspect 13. The device of any one of aspects 11 to 12, wherein thedifference between the minimum bandgap and the maximum bandgap is from100 meV to 600 meV.

Aspect 14. The device of any one of aspects 11 to 12, wherein thedifference between the minimum bandgap and the maximum bandgap is from400 meV to 600 meV.

Aspect 15. The device of any one of aspects 11 to 12, wherein thedifference between the minimum bandgap and the maximum bandgap is from200 meV to 500 meV.

Aspect 16. The device of any one of aspects 1 to 10, wherein, themultiplication layer comprises one or more interlayers wherein each ofthe interlayers comprises Ga_(1-x)In_(x)N_(y)As_(1-y-z)(Sb,Bi)_(z); andthe multiplication layer is characterized by a minimum bandgap and amaximum bandgap.

Aspect 17. The device of aspect 16, wherein at least one or moreinterlayers has a linearly graded bandgap across the interlayerthickness.

Aspect 18. The device of any one of aspects 16 to 17, wherein theminimum bandgap is within a range from 0.7 eV to 1.3 eV and the maximumbandgap is within a range from 0.8 eV to 1.42 eV.

Aspect 19. The device of any one of aspects 16 to 18, wherein thedifference between the minimum bandgap and the maximum bandgap is from100 meV to 600 meV.

Aspect 20. The device of any one of aspects 16 to 18, wherein thedifference between the minimum bandgap and the maximum bandgap is from400 meV to 600 meV.

Aspect 21. The device of any one of aspects 16 to 18, wherein thedifference between the minimum bandgap and the maximum bandgap is from200 meV to 500 meV.

Aspect 22. The device of any one of aspects 16 to 21, wherein theGa_(1-x)In_(x)N_(y)As_(1-y-z)(Sb,Bi)_(z) composition of the linearlygraded interlayer varies from 0≤x≤0.4, 0≤y≤0.07 and 0<z≤0.2, to 0≤x≤0.4,0≤y≤0.07, and 0<z≤0.2.

Aspect 23. The device of any one of aspects 1 to 10, wherein, themultiplication layer comprises two or more interlayers; and at least oneof the two or more interlayers comprises a constant bandgap across thethickness of the interlayer.

Aspect 24. The device of claim 23, wherein each of the two or moreinterlayers has a constant bandgap across the interlayer thickness.

Aspect 25. The device of any one of aspects 1 to 10, wherein themultiplication layer comprises: a first interlayer comprising a firstGa_(1-x1)In_(x1)N_(y1)As_(1-y1-z1)(Sb,Bi)_(z1) composition; and a secondinterlayer comprising a secondGa_(1-x2)In_(x2)N_(y2)As_(1-y2-z2)(Sb,Bi)_(z2) composition, wherein thefirst Ga_(1-x1)In_(x1)N_(y1)As_(1-y1-z1)(Sb,Bi)_(z1) composition isdifferent than the second Ga_(1-x2)In_(x2)N_(y2)As_(1-y2-z2)(Sb,Bi)_(z2)composition; and wherein each of the first interlayer and the secondinterlayer have a constant bandgap across the thickness of therespective interlayer.

Aspect 26. The device of aspect 25, wherein, the firstGa_(1-x1)In_(x1)N_(y1)As_(1-y1-z1)(Sb,Bi)_(z1) composition has a firstbandgap within a range from 0.7 eV to 1.3 eV; and the secondGa_(1-x2)In_(x2)N_(y2)As_(1-y2-z2)(Sb,Bi)_(z2) composition has a secondbandgap within a range from 0.8 eV to 1.42 eV.

Aspect 27. The device of any one of aspects 25 to 26, wherein thedifference between the first bandgap and the second bandgap is from 100meV to 600 meV.

Aspect 28. The device of any one of aspects 25 to 26, wherein thedifference between the first bandgap and the second bandgap is from 400meV to 600 meV.

Aspect 29. The device of any one of aspects 25 to 26, wherein thedifference between the first bandgap and the second bandgap is from 200meV to 500 meV.

Aspect 30. The device of any one of aspects 25 to 29, wherein, the firstGa_(1-x1)In_(x1)N_(y1)As_(1-y1-z1)(Sb,Bi)_(z1) composition is 0≤x1≤0.4,0≤y1≤0.07 and 0<z1≤0.2; and the secondGa_(1-x2)In_(x2)N_(y2)As_(1-y2-z2)(Sb,Bi)_(z2) composition is 0≤x2≤0.4,0≤y2≤0.07, and 0<z2≤0.2.

Aspect 31. The device of any one of aspects 1 to 10, wherein themultiplication layer comprises a superlattice structure.

Aspect 32. The device of aspect 31, wherein the superlattice comprises astepped superlattice.

Aspect 33. The device of aspect 32, wherein the stepped superlatticecomprises a periodic superlattice.

Aspect 34. The device of aspect 32, wherein the stepped superlatticecomprises a staircase superlattice.

Aspect 35. The device of claim 31, wherein the superlattice comprises alinearly graded superlattice.

Aspect 36. The device of any one of aspects 1 to 35, wherein the devicecomprises an avalanche photodetector

Aspect 37. A method of forming a semiconductor optoelectronic device,comprising: forming a first barrier layer overlying a substrate; forminga multiplication layer overlying the first barrier layer, wherein themultiplication layer comprises Ga_(1-x)In_(x)N_(y)As_(1-y-z)(Sb,Bi)_(z),wherein 0≤x≤0.4, 0≤y≤0.07, and 0<z≤0.2; forming an active layeroverlying the multiplication layer, wherein, the active layer comprisesa pseudomorphic dilute nitride material; and the dilute nitride materialhas a bandgap within a range from 0.7 eV and 1.2 eV; and forming asecond barrier layer overlying the active layer.

Aspect 38. The method of aspect 37, further comprising: after formingthe multiplication layer, forming a charge layer overlying themultiplication layer; and forming the active layer comprises forming theactive layer overlying the charge layer.

EXAMPLES

To assess GaInNAsSb materials quality, GaInNAsSb layers were grown onundoped GaAs, with thicknesses within a range from 250 nm and 2 μm. TheGaInNAsSb layers were capped with GaAs. Time-resolved photoluminescence(TRPL) measurements was performed to determine the minority carrierlifetime of the GaInNAsSb layer. The TRPL kinetics were measured at anexcitation wavelength of 970 nm, with an average CW power of 0.250 mW,and a pulse duration of 200 fs generated by a Ti:Sapphire:OPA laser. Thepulse repetition rate was 250 kHz. The laser beam diameter at the samplewas approximately 1 mm. Whereas dilute nitride materials have beenreported with minority carrier lifetimes below 1 ns, materials accordingto the present invention have higher carrier lifetime values, withcarrier lifetimes between approximately 1.1 ns and 2.5 ns. CertainGaInNAsSb layers exhibited a minority carrier lifetime greater than 2ns. Carrier lifetime can be affected by background doping levels andother defects that can be present in a material. The carrier lifetimesare therefore indicative of good materials quality, and can lead toimproved performance of both absorber and multiplication layers ofdevices.

Finally, it should be noted that there are alternative ways ofimplementing the embodiments disclosed herein. Accordingly, the presentembodiments are to be considered as illustrative and not restrictive.Furthermore, the claims are not to be limited to the details givenherein, and are entitled their full scope and equivalents thereof.

1. A semiconductor optoelectronic device, comprising: a substrate; afirst barrier layer overlying the substrate; a multiplication layeroverlying the first barrier layer; wherein the multiplication layercomprises Ga_(1-x)In_(x)N_(y)As_(1-y-z)(Sb,Bi)_(z), wherein 0≤x≤0.4,0≤y≤0.07, and 0≤z≤0.2. an active layer overlying the multiplicationlayer, wherein, the active layer comprises a lattice matched orpseudomorphic dilute nitride material; and the dilute nitride materialhas a bandgap within a range from 0.7 eV and 1.2 eV; and a secondbarrier layer overlying the active layer.
 2. The device of claim 1,wherein each of the first barrier layer and the second barrier layerindependently comprises a doped III-V material.
 3. The device of claim1, wherein the substrate comprises GaAs, AlGaAs, Ge, SiGeSn, or bufferedSi.
 4. The device of claim 1, further comprising a charge layeroverlying the multiplication layer and underlying the active layer. 5.The device of claim 1, wherein the active layer comprises GaInNAs,GaNAsSb, GaInNAsSb, GaInNAsBi, GaNAsSbBi, GaNAsBi, or GaInNAsSbBi. 6.The device of claim 1, wherein the active layer comprisesGa_(1-x)In_(x)N_(y)As_(1-y-z)(Sb,Bi)_(z), wherein 0≤x≤0.4, 0<y≤0.07, and0<z≤0.2.
 7. The device of claim 1, wherein the multiplication layercomprises a linearly graded bandgap across the thickness of the layerand is characterized by a minimum bandgap and a maximum bandgap.
 8. Thedevice of claim 7, wherein the minimum bandgap is within a range from0.7 eV to 1.3 eV and the maximum bandgap is within a range from 0.8 eVto 1.42 eV.
 9. The device of claim 7, wherein the difference between theminimum bandgap and the maximum bandgap is from 100 meV to 600 meV. 10.The device of claim 1, wherein, the multiplication layer comprises oneor more interlayers wherein each of the interlayers comprisesGa_(1-x)In_(x)N_(y)As_(1-y-z)(Sb,Bi)_(z); and the multiplication layeris characterized by a minimum bandgap and a maximum bandgap.
 11. Thedevice of claim 10, wherein at least one or more interlayers has alinearly graded bandgap across the interlayer thickness.
 12. The deviceof claim 10, wherein the minimum bandgap is within a range from 0.7 eVto 1.3 eV and the maximum bandgap is within a range from 0.8 eV to 1.42eV.
 13. The device of claim 10, wherein the difference between theminimum bandgap and the maximum bandgap is from 100 meV to 600 meV. 14.The device of claim 10, wherein theGa_(1-x)In_(x)N_(y)As_(1-y-z)(Sb,Bi)_(z) composition of the linearlygraded interlayer varies from 0≤x≤0.4, 0≤y≤0.07 and 0<z≤0.2, to 0≤x≤0.4,0≤y≤0.07, and 0<z≤0.2.
 15. The device of claim 1, wherein, themultiplication layer comprises two or more interlayers; and at least oneof the two or more interlayers comprises a constant bandgap across thethickness of the interlayer.
 16. The device of claim 15, wherein each ofthe two or more interlayers has a constant bandgap across the interlayerthickness.
 17. The device of claim 1, wherein the multiplication layercomprises: a first interlayer comprising a firstGa_(1-x1)In_(x1)N_(y1)As_(1-y1-z1)(Sb,Bi)_(z1) composition; and a secondinterlayer comprising a secondGa_(1-x2)In₂N_(y2)As_(1-y2-z2)(Sb,Bi)_(z2) composition, wherein thefirst Ga_(1-x1)In_(x1)N_(y1)As_(1-y1-z1)(Sb,Bi)_(z1) composition isdifferent than the second Ga_(1-x2)In_(x2)N_(y2)As_(1-y2-z2)(Sb,Bi)_(z2)composition; and wherein each of the first interlayer and the secondinterlayer have a constant bandgap across the thickness of therespective interlayer.
 18. The device of claim 17, wherein, the firstGa_(1-x1)In_(x1)N_(y1)As_(1-y1-z1)(Sb,Bi)_(z1) composition has a firstbandgap within a range from 0.7 eV to 1.3 eV; and the secondGa_(1-x2)In_(x2)N_(y2)As_(1-y2-z2)(Sb,Bi)_(z2) composition has a secondbandgap within a range from 0.8 eV to 1.42 eV.
 19. The device of claim18, wherein the difference between the first bandgap and the secondbandgap is from 100 meV to 600 meV.
 20. The device of claim 18, wherein,the first Ga_(1-x1)In_(x1)N_(y1)As_(1-y1-z1)(Sb,Bi)_(z1) composition is0≤x1≤0.4, 0≤y1≤0.07 and 0<z1≤0.2; and the secondGa_(1-x2)In_(x2)N_(y2)As_(1-y2-z2)(Sb,Bi)_(z2) composition is 0≤x2≤0.4,0≤y2≤0.07, and 0<z2≤0.2.
 21. The device of claim 1, wherein themultiplication layer comprises a superlattice structure.
 22. The deviceof claim 1, wherein the device comprises an avalanche photodetector 23.A method of forming a semiconductor optoelectronic device, comprising:forming a first barrier layer overlying a substrate; forming amultiplication layer overlying the first barrier layer, wherein themultiplication layer comprises Ga_(1-x)In_(x)N_(y)As_(1-y-z)(Sb,Bi)_(z),wherein 0≤x≤0.4, 0≤y≤0.07, and 0<z≤0.2; forming an active layeroverlying the multiplication layer, wherein, the active layer comprisesa pseudomorphic dilute nitride material; and the dilute nitride materialhas a bandgap within a range from 0.7 eV and 1.2 eV; and forming asecond barrier layer overlying the active layer.